U.S. patent application number 17/079653 was filed with the patent office on 2021-02-11 for resolver signal processing circuit.
The applicant listed for this patent is DENSO CORPORATION. Invention is credited to Shinichiro NAKATA, Makoto OISHI, Hirokazu SADAMATSU.
Application Number | 20210041508 17/079653 |
Document ID | / |
Family ID | 1000005219083 |
Filed Date | 2021-02-11 |
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United States Patent
Application |
20210041508 |
Kind Code |
A1 |
SADAMATSU; Hirokazu ; et
al. |
February 11, 2021 |
RESOLVER SIGNAL PROCESSING CIRCUIT
Abstract
A resolver signal processing circuit for amplifying two phase
signals output from a resolver includes first and second amplifier
circuits configured to adjust an input in-phase voltage range to
output an intended voltage even when a short-circuit arises in the
resolver. The resolver signal processing circuit further includes
first and second short-circuit detection circuits configured to
detect the short-circuit arising in the resolver and short-circuits
in first and second signal input paths from the resolver to the
first and the second amplifier circuits, respectively, and first
and second voltage adjusting units configured to adjust input
in-phase voltage ranges of the first and second amplifier circuits
when the first and second short-circuit detection circuits detect
short-circuits, respectively. The first and second amplifier
circuits are configured to adjust the input in-phase voltage
ranges, respectively.
Inventors: |
SADAMATSU; Hirokazu;
(Kariya-city, JP) ; NAKATA; Shinichiro;
(Kariya-city, JP) ; OISHI; Makoto; (Toyota-shi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DENSO CORPORATION |
Kariya-city |
|
JP |
|
|
Family ID: |
1000005219083 |
Appl. No.: |
17/079653 |
Filed: |
October 26, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2019/015441 |
Apr 9, 2019 |
|
|
|
17079653 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H03F 3/45 20130101; G01R
31/52 20200101; H03M 1/645 20130101 |
International
Class: |
G01R 31/52 20060101
G01R031/52; H03F 3/45 20060101 H03F003/45; H03M 1/64 20060101
H03M001/64 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 19, 2018 |
JP |
2018-116196 |
Claims
1. A resolver signal processing circuit for amplifying two phase
signals output from a resolver, the resolver signal processing
circuit comprising: first and second amplifier circuits configured
to adjust an input in-phase voltage range to output an intended
voltage even when a short-circuit arises in the resolver.
2. The resolver signal processing circuit according to claim 1,
further comprising: first and second short-circuit detection
circuits configured to detect the short-circuit arising in the
resolver and short-circuits in first and second signal input paths
from the resolver to the first and the second amplifier circuits,
respectively; and first and second voltage adjusting units
configured to adjust input in-phase voltage ranges of the first and
second amplifier circuits when the first and second short-circuit
detection circuits detect short-circuits, respectively, wherein the
first and second amplifier circuits are configured to adjust the
input in-phase voltage ranges, respectively.
3. The resolver signal processing circuit according to claim 2,
wherein: each of the first and second amplifier circuits is
configured by a differential amplifier circuit using an operational
amplifier; and each of the first and second voltage adjusting units
is configured to change the input in-phase voltage range of the
differential amplifier circuit.
4. The resolver signal processing circuit according to claim 2,
wherein: the first and second amplifier circuits include first and
second voltage dividing circuits configured to divide the two-phase
signals respectively, first and second A/D converters configured to
convert voltages divided by the first and second voltage dividing
circuits into digital data respectively, and first and second gain
setting units configured to multiply the digital data of the first
and second A/D converters by gains set in accordance with
amplification ratios respectively; and the first and second voltage
adjusting units change voltage dividing states of the first and
second voltage dividing circuits, respectively.
5. The resolver signal processing circuit according to claim 2,
wherein: the first and second short-circuit detection circuits are
configured to detect the short-circuit in windings of the resolver,
the short-circuit of the first and second input paths to a power
supply and to a ground, respectively; and the first and second
voltage adjusting units are configured to change the input in-phase
voltage ranges of the first and second amplifier circuits in
correspondence to a type of the short-circuit detected by the first
and second short-circuit detection circuits, respectively.
6. The resolver signal processing circuit according to claim 3,
wherein: the first and second short-circuit detection circuits are
configured to detect the short circuit in windings of the resolver,
the short-circuit of the first and second input paths to a power
supply and to a ground, respectively; and the first and second
voltage adjusting units are configured to change the input in-phase
voltage ranges of the first and second amplifier circuits in
correspondence to a type of the short-circuit detected by the first
and second short-circuit detection circuits, respectively.
7. The resolver signal processing circuit according to claim 4,
wherein: the first and second short-circuit detection circuits are
configured to detect the short circuit in windings of the resolver,
the short-circuit of the first and second input paths to a power
supply and to a ground, respectively; and the first and second
voltage adjusting units are configured to change the input in-phase
voltage ranges of the first and second amplifier circuits in
correspondence to a type of the short-circuit detected by the first
and second short-circuit detection circuits, respectively.
8. A resolver signal processing circuit for amplifying two phase
signals output from a resolver attached to a motor, the resolver
signal processing circuit comprising: a differential amplifier; a
plurality of resistor groups connected between the resolver and the
differential amplifier and configured to vary a voltage input from
the resolver to the differential amplifier in response to a
diagnostic signal applied thereto, each of the resistor groups
including resistors and switches; and a control unit configured to
determine a rotation angle of the motor based on an output signal
of the differential amplifier, determine a short-circuit state
including a short-circuit in the resolver, a short-circuit of the
signal input path to a power supply and a short-circuit of the
signal input path to a ground, and control on-off states of the
switches in the plurality of resistor groups to vary resistances of
the plurality of resistor groups and thereby vary an input voltage
range of the differential amplifier in correspondence to a
determined short-circuit state.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation application of
International Patent Application No. PCT/JP2019/015441 filed on
Apr. 9, 2019, which designated the U.S. and claims the benefit of
priority of Japanese Patent Application No. 2018-116196 filed on
Jun. 19, 2018. The entire disclosures of both applications are
incorporated herein by reference.
FIELD
[0002] The present disclosure relates to a circuit that processes a
signal output from a resolver.
BACKGROUND
[0003] As one method of motor rotation angle detection, two-phase
signals output from a resolver is used. According to this detection
method, the two-phase signals are differentially input, amplified
to differential type signals SINO and COSO respectively and input
to a control circuit such as a microcomputer for signal processing
to detect the motor rotation angle.
SUMMARY
[0004] The present disclosure addresses the above problem and has
an object to provide a resolver signal processing circuit that
maintains a detection accuracy of a rotation angle even when a
short-circuit arises in an input path of a signal output from a
resolver.
[0005] According to the present disclosure, first and second
amplifier circuits amplify two-phase signals output from a
resolver, respectively, and output intended voltages by regulating
an input in-phase voltage range when a short-circuit arises in the
resolver. That is, the input in-phase voltage range is limited so
that the output voltage is not affected. Thereby, even when a
short-circuit arises in the resolver, the rotation angle can be
detected based on the two-phase signals.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] The above and other objects, features and advantages of the
present disclosure will become more apparent from the following
detailed description made with reference to the accompanying
drawings. In the drawings:
[0007] FIG. 1 is a circuit diagram showing a configuration of a
resolver signal processing circuit according to a first
embodiment;
[0008] FIG. 2 is a flowchart showing processing contents of an
MCU;
[0009] FIG. 3 is a circuit diagram showing a resistor connection
state at the time of REF short-circuit;
[0010] FIG. 4 is a waveform diagram showing an output voltage
waveform of a differential amplifier circuit corresponding to the
state shown in FIG. 3;
[0011] FIG. 5 is a circuit diagram showing a resistor connection
state at the time of a power short-circuit;
[0012] FIG. 6 is a waveform diagram showing an output voltage
waveform of a differential amplifier circuit corresponding to the
state shown in FIG. 5;
[0013] FIG. 7 is a circuit diagram showing a resistor connection
state at the time of a ground short-circuit;
[0014] FIG. 8 is a waveform diagram showing an output voltage
waveform of a differential amplifier circuit corresponding to the
state shown in FIG. 7;
[0015] FIG. 9 is a circuit diagram showing a configuration of a
resolver signal processing circuit according to a second
embodiment;
[0016] FIG. 10 is a circuit diagram showing a voltage dividing
state during a normal operation;
[0017] FIG. 11 is a waveform diagram showing an output voltage
waveform of a digital signal processing unit corresponding to the
state shown in FIG. 10;
[0018] FIG. 12 is a circuit diagram showing a voltage dividing
state at the time of a REF short-circuit;
[0019] FIG. 13 is a waveform diagram showing an output voltage
waveform of a digital signal processing unit corresponding to the
state shown in FIG. 12;
[0020] FIG. 14 is a circuit diagram showing a resistor connection
state at the time of a power short-circuit;
[0021] FIG. 15 is a waveform diagram showing an output voltage
waveform of a differential amplifier circuit corresponding to the
state shown in FIG. 14;
[0022] FIG. 16 is a circuit diagram showing a resistor connection
state at the time of a ground short-circuit;
[0023] FIG. 17 is a waveform diagram showing an output voltage
waveform of a differential amplifier circuit corresponding to the
state shown in FIG. 16;
[0024] FIG. 18 is a circuit diagram showing a configuration of a
resolver signal processing circuit according to a third
embodiment;
[0025] FIG. 19 is a diagram showing output voltage waveforms of the
differential amplifier circuit at the time of normal operation and
a REF short-circuit, and
[0026] FIG. 20 is a waveform diagram showing an output voltage
waveform of a differential amplifier circuit at the time of normal
operation and REF short-circuit.
DETAILED DESCRIPTION OF THE EMBODIMENT
First Embodiment
[0027] Referring first to FIG. 1, a resolver 1 includes a primary
winding 2 and two secondary windings 3S, 3C. These windings 2 and 3
are insulated from each other. An excitation circuit (not shown)
that supplies an excitation signal is connected to the primary
winding 2. The secondary winding 3S outputs a SIN (sine) phase
signal, and the secondary winding 3C outputs a COS (cosine) phase
signal.
[0028] The primary winding 2 is connected to a rotor of a motor
(not shown) whose rotation angle is to be detected. A mutual
inductance between each of the secondary windings 3S, 3C and the
primary winding 2 periodically changes according to a rotation
angle .theta. of the rotor of the motor. As a result, output
voltages of the secondary windings 3S and 3C become modulated waves
produced by modulating the excitation signal with modulating waves
SINO and COSO, respectively. The resolver 1 is mounted on a vehicle
to detect the rotation angle of a drive motor for travel of an
electric vehicle, for example.
[0029] One end and the other end of the secondary winding 3S are
connected to signal lines SINP and SINN, respectively. A bias
circuit 4S and a short-circuit detection circuit 5S are connected
in parallel between the signal lines SINP and SINN. The bias
circuit 4S applies a bias voltage that sets a center voltage of a
resolver signal. The short-circuit detection circuit 5S is a
resistor voltage dividing circuit for detecting a short-circuit on
the SINO side, and a divided voltage output thereof is input to a
short-circuit state determination circuit 7S inside an MCU 6 via an
input terminal SINDET of the MCU 6.
[0030] The signal lines SINP and SINN are connected to respective
input terminals of a differential amplifier circuit 8S. The
differential amplifier circuit 8S is mainly composed of an
operational amplifier 9S. Between the signal lines SINP, SINN and a
non-inverting input terminal and an inverting input terminal of the
operational amplifier 9S, a resistor R1 group including a plurality
of series-connected resistors R1 is connected. A switch SW1 for
short-circuiting is connected in parallel to a part of the
resistors R1.
[0031] Between a power supply V1 and the non-inverting input
terminal of the operational amplifier 9S, a resistor R2 is
connected in series to a parallel circuit of a resistor R3 group
and a resistor R4 group. The resistor R3 group has a configuration
in which a plurality of series circuits of a resistor R3 and a
switch SW3 are connected in parallel. The resistor R4 group also
has a configuration in which a plurality of series circuits of a
resistor R4 and a switch SW4 are connected in parallel. However, in
the resistor R4 group, only one resistor R4 is connected in
parallel to the series circuits. A switch SW2 for short-circuiting
the resistor R2 is connected in parallel to the resistor R2.
[0032] Further, between the power supply V1 and the inverting input
terminal of the operational amplifier 9S, the same series circuit
of resistor R3 group and a resistor R2 as that on the non-inverting
input terminal side is connected in series. The resistor R4 group
is connected between an output terminal of the operational
amplifier 9S and the resistor R2. It is noted that reference
numerals and symbols are attached to only some of the circuit
elements in order to avoid complication of the drawing. The output
terminal of the operational amplifier 9S is connected to an input
terminal of a motor rotation angle estimation unit 10 inside the
MCU 6 via an input terminal SINO of the MCU 6. The configuration on
the COS phase side is symmetrical to that on the SIN phase side.
Hence, the corresponding configuration is indicated by "C"
indicating a cosine signal path system instead of "S" indicating a
sine signal path system in FIG. 1. The sine signal path system and
the cosine signal path system form a first signal system and a
second signal system, respectively. Structural components in the
first signal system and the second signal system are identified
with first and second, respectively, when necessary.
[0033] The motor rotation angle estimation unit 10 is configured to
receive the output signals SINO and COSO of the differential
amplifier circuits 8S and 8C and estimate the rotation angle of the
motor. The short-circuit state determination circuits 7S and 7C are
configured to determine whether a short-circuit state is present by
receiving the input signals of the short-circuit detection circuits
5S and 5C and further determine a type of the short-circuit, that
is, whether the short-circuit is a short-circuit to REF (referred
to as a REF short-circuit or REF-short), a short-circuit to a power
supply (referred to as a power short-circuit or power-short) or a
short-circuit to a ground (referred to as a ground short-circuit or
ground-short), when a short-circuit is arises. The REF
short-circuit means a short-circuit among the primary and secondary
windings 2, 3S and 3C in the resolver 1.
[0034] When a short-circuit arises, the short-circuit state
determination circuits 7S and 7C respectively output diagnostic
signals SINDIAG and COSDIAG according to the type of the
short-circuit, and change on-off states of the switches SW1 to SW4
of the differential amplifier circuits 8S and 8C. That is, the
diagnostic signals SINDIAG and COSDIAG indicate the type of
short-circuit by 2-bit data. The short-circuit detection circuit 5
and the short-circuit state determination circuit 7 operate as a
short-circuit detection circuit. Moreover, the short-circuit state
determination circuit 7 operates as a voltage adjusting unit.
[0035] Next, operation of the present embodiment will be described.
In the following description, "S" and "C" indicating the sine
signal system and the cosine signal system are not used because
both signal systems operate similarly. As shown in FIG. 2, the
short-circuit state determination circuit 7 acquires a detection
voltage (DET voltage) of the short-circuit detection circuit 4 and
compares it with a normal threshold value (step S1), a power
short-circuit threshold value (step S2), and a ground short-circuit
threshold value (step S3), respectively. In case a circuit
operating power supply voltage is 5V, for example, the normal
threshold value is about 2.5V, the power short-circuit threshold
value is 5V, and the ground short-circuit threshold value is 0V. If
the DET voltage is equal to the normal threshold value, a normal
signal is output (step S7). For example, the 2-bit data of the
diagnostic signal is set to "00" indicating no short-circuit to
make the diagnosis detection inactive.
[0036] If the DET voltage is different from the normal threshold
value and equal to the power short-circuit threshold value, the
2-bit data of the diagnostic signal is set to "01," for example, to
output a diagnostic signal indicating the power short-circuit
detection (step S6). If the DET voltage is different from the power
short-circuit threshold value and equal to the ground short-circuit
threshold value, the 2-bit data of the diagnostic signal to "10,"
for example, to output a diagnostic signal indicating the ground
short-circuit detection (step S5). Further, if the DET voltage is
different from the power short-circuit threshold value, the 2-bit
data of the diagnostic signal is set to "11," for example, to
output a diagnostic signal indicating the REF short-circuit
detection (step S4).
[0037] In the present embodiment, each of the above three resistor
groups R1, R3 and R4 each have a three-element configuration.
[0038] <Normal Operation Time>
[0039] At the time of normal operation (step S7) shown in FIG. 1,
each switch SW is controlled as follows:
[0040] one switch SW1 in the resistor R1 group is turned on;
[0041] the switch SW2 of the resistor R2 is turned on;
[0042] all switches SW3 in the resistor R3 group are turned off;
and
[0043] all switches SW4 in the resistor R4 group are turned
off.
[0044] At this time, an input-output gain G0 of the operational
amplifier 9 is given as follows.
G0=R4/(2.times.R1).
Therefore, an input voltage VINP0 of the operational amplifier 9S
is given as follows.
VINP=V1-2.times.R1/(2.times.R1+R2+R4).times.(V1-VSINP)
[0045] <REF Short-Circuit Time>
[0046] At the time of REF short-circuit (step S4) shown in FIG. 3,
each switch SW is controlled as follows:
[0047] all switches SW1 in the resistor R1 group are turned
off:
[0048] the switch SW2 of the resistor R2 is turned off;
[0049] one switch SW3 in the resistor R3 group is turned on;
and
[0050] one switch SW4 in the resistor R4 group is turned on.
At this time, an input-output gain G1 of the operational amplifier
9 is given as follows.
G1={R2+R3//(R4/2)}/(3.times.R1)
An input voltage VINP1 of the operational amplifier 9S is given as
follows.
VINP1=V1-3.times.R1/{3.times.R1+R2+R3//(R4/2)}.times.(V1-VSINP)
[0051] Here, it is assumed that, as shown in FIG. 4, the REF
voltage is 2.5 V, and the SIN phase signal and the COS phase signal
both have an amplitude of the REF voltage .+-.1.295 V at the
normally operating time. When the REF short-circuit arises in this
state, the amplitudes of the positive phase signal (normal phase
signal) and the negative phase signal (reverse phase signal) of the
SIN phase signal and the COS phase signal are as follows:
[0052] the positive phase signal is 0V.+-.10.73V; and
[0053] the negative phase signal is 0V.+-.13.32V.
Further, both signals are in-phase (common mode phase, that is,
same phase).
[0054] On the other hand, by adjusting the input in-phase voltage
range of the operational amplifier 9 in step S4, it is possible to
prevent the output voltage waveform of the operational amplifier 9
from being distorted. Therefore, the MCU 6 can detect the rotation
angle based on the two-phase signals as in the normal time.
[0055] <Power Short-Circuit Time>
[0056] As shown in FIG. 5, each switch SW is controlled as follows
at the time of the power short-circuit (step S6):
[0057] All switches SW1 in the resistor R1 group are turned
off:
[0058] the switch SW2 of the resistor R2 is turned off;
[0059] two switches SW3 in the resistor R3 group are turned on;
and
[0060] one switch SW4 in the resistor R4 group is turned on.
As shown in FIG. 6, at the time of the power short-circuit, the REF
voltage rises to, for example, a battery voltage +B of a vehicle or
to a boosted power supply voltage when a voltage boosting operation
is performed. On the other hand, by adjusting the input in-phase
voltage range as described above, the output voltage waveform of
the operational amplifier 9 is prevented from being distorted.
[0061] <Ground Short-Circuit Time>
[0062] At the time of the ground short-circuit time (step S5) shown
in FIG. 7, each switch SW is controlled as follows:
[0063] all switches SW1 in the first resistor R1 group are turned
on;
[0064] the switch SW2 of the resistor R2 is turned off;
[0065] all switches SW3 in the resistor R3 group are turned on;
and
[0066] all switches SW4 in the resistor R4 group are turned on.
As shown in FIG. 8, at the ground short-circuit time, the REF
voltage drops to 0V. However, by adjusting the input in-phase
voltage range as described above, the MCU 6 can detect the rotation
angle based on the two-phase signals as in the normal operation
time.
[0067] As described above, according to the present embodiment, the
short-circuit state determination circuits 7S and 7C respectively
detect that a short-circuit has occurred in the resolver 1 or in
the signal input path from the resolver 1 to the differential
amplifier circuits 8S and 8C. When each short-circuit state
determination circuit 7S, 7C detects the short-circuit, the input
in-phase voltage range of the corresponding amplifier circuits 8S,
8C is changed. It is thus possible to dynamically limit the input
in-phase voltage range so that the output voltage is not affected
by the short-circuit. Since the MCU 6 can thus detect the rotation
angle of the motor based on the two-phase signals as in the normal
state, the electric vehicle can travel in the same manner as in the
normal state and a limp-home traveling can be performed at high
speed.
[0068] Further, the short-circuit state determination circuits 7S
and 7C detect the winding short-circuit that occurs in the resolver
1 and the power short-circuit and the ground short-circuit that
occur in the input path, and change the input in-phase voltage
range of the differential amplifier circuits 8S and 8C. This input
voltage range change can prevent the output voltage of the
amplifier circuit 8 from being affected in each short-circuit
case.
[0069] It is noted that, when a short-circuit of a winding arises
in a resolver, the amplitude of the signal (SINO/COSO) used to
detect the rotation angle increase. In this situation, as shown in
FIG. 20, a signal waveform distorts. As a result, a sum of squares
of a sine signal and a cosine signal does not become "1," and the
detection accuracy of the rotation angle is lowered. The first
embodiment described above obviates this deficiency of the prior
art.
Second Embodiment
[0070] Hereinafter, the identical parts as those in the first
embodiment will be designated by the same reference numerals for
simplification of the description. Only differences from the first
embodiment will be described below. As shown in FIG. 9, in a second
embodiment, digital signal processing units 11S and 11C are
arranged in place of the differential amplifier circuits 8S and 8C.
The digital signal processing unit 11 (S, C) includes an A/D
converter 12, a gain calculation unit 13 and a D/A converter 14.
The digital signal processing units 11S and 11C correspond to first
and second amplifier circuits, respectively. The gain calculation
unit 13 corresponds to a gain setting unit.
[0071] For example, as shown in FIG. 10, a voltage dividing circuit
15 (S, C) capable of changing a voltage dividing ratio of the input
voltage is arranged on an input side of the A/D converter 12. A
series circuit of resistors Ra and Rb is connected between a
terminal T to which a voltage of each phase signal is applied and
an input terminal VIN of the A/D converter 12. A series circuit of
a resistor Rc and a switch SW40 is connected between the input
terminal VIN and a changeover switch SW50.
[0072] Switches SW10 and SW20 are connected in parallel to the
resistors Ra and Rb, respectively. A series circuit of a switch
SW30 and a resistor Rd is connected in parallel to the resistor Rc.
The changeover switch SW50 is provided to be connected to the power
supply voltage V1 or the ground. The switches SW10 to SW50 are
controlled by the signals SINDIAG and COSDIAG output from the
short-circuit state determination circuits 7S and 7C to adjust the
voltage division state in the voltage dividing circuit 15.
[0073] Operation of the second embodiment will be described
next.
[0074] <Normal Operation Time>
[0075] As shown in FIG. 10, during a normal operation time, the
switches SW10 to SW50 are controlled as follows:
[0076] the switch SW10 is turned on;
[0077] the switch SW20 is turned on;
[0078] the switch SW30 is turned on or off;
[0079] the switch SW40 is turned off; and
[0080] the switch SW50 is turned on or off.
At this time, the voltage of the input terminal VIN is not divided
and changes around the voltage V1 as shown in FIG. 11.
[0081] <REF Short-Circuit Time>
[0082] As shown in FIG. 12, each of the switches SW10 to SW50 is
controlled as follows during the REF short-circuit time:
[0083] the switch SW10 is turned off;
[0084] the switch SW20 is turned on;
[0085] the switch SW30 is turned off;
[0086] the switch SW40 is turned on; and
[0087] the switch SW50 is turned to the voltage V1.
That is, as shown in FIG. 13, the voltage is divided by the ratio
Rc/(Ra+Rc) with reference to the voltage V1 so that the voltage
applied to the input terminal VIN does not become negative.
[0088] <Power Short-Circuit Time>
[0089] As shown in FIG. 14, each of the switches SW10 to SW50 is
controlled as follows during the power short-circuit time:
[0090] the switch SW10 is turned off;
[0091] the switch SW20 is turned on;
[0092] the switch SW30 is turned on.
[0093] the switch SW40 is turned on; and
[0094] the switch SW50 is turned to the ground GND.
That is, as shown in FIG. 15, the voltage is divided by the ratio
of Rc/(Ra+Rc//Rd) with reference to the ground so that the voltage
applied to the input terminal VIN does not exceed the power supply
voltage.
[0095] <Ground Short-Circuit Time>
[0096] As shown in FIG. 16, each of the switches SW10 to SW50 is
controlled as follows during the ground short-circuit time:
[0097] the switch SW10 is turned off;
[0098] the switch SW20 is turned off;
[0099] the switch SW30 is turned on.
[0100] the switch SW40 is turned on; and
[0101] the switch SW50 is turned to the voltage V1.
That is, as shown in FIG. 17, the voltage V1 is divided by the
ratio Rc//Rd/(Ra+Rb+Rc//Rd) with reference to the voltage V1 so
that the voltage applied to the input terminal VIN does not become
negative.
[0102] As described above, according to the second embodiment, the
digital signal processing units 11S and 11C include the voltage
dividing circuits 15S and 15C that divide the two-phase signals,
respectively, the A/D converters 12S and 12C that convert the
divided voltages into the digital data, respectively, and the gain
calculation units 13S and 13C that multiply the A/D converted data
by a gain according to the amplification factor, respectively. The
short-circuit state determination circuits 7S and 7C change the
voltage division state in the voltage dividing circuits 15S and
15C, respectively. With this configuration, the same effect as that
of the first embodiment can be provided even in case the two-phase
signals are processed as digital data.
[0103] As shown in FIG. 18, according to a third embodiment, a
differential amplifier circuits 21S and 21C are provided in place
of the differential amplifier circuits 8S and 8C, respectively. In
the present embodiment, the connection state of each resistor
connected to the operational amplifier 9 is fixed. Each of the
resistors R1 to R4 is formed of one resistance element. Except the
resistor R4 whose one end is connected to the output terminal of
the operational amplifier 9, the circuit configuration is in the
same connection state as in the REF short-circuit case of the first
embodiment. Therefore, the MCU 6 does not output the signals
SINDIAG and COSDIAG.
[0104] Next, operation of the third embodiment will be described.
In the third embodiment, the circuit configuration is determined to
meet only the REF-short circuit. Therefore, as shown in FIG. 19,
even if the REF short-circuit arises in the normal operation state,
the signal waveform of the output signal of the differential
amplifier circuit 21 is not distorted as in the case shown in FIG.
4 of the first embodiment.
[0105] As described above, according to the third embodiment, the
input in-phase voltage range in the differential amplifier circuits
21S and 21C is limited so that the output voltage is not affected
when the REF short-circuit arises in the resolver 1. Therefore,
when the MCU 6 detects the occurrence of the REF short-circuit, it
is not necessary to switch the connection state of each resistor as
opposed to the first embodiment.
Other Embodiment
[0106] The number of resistors in each resistor group in the first
embodiment, the number of the voltage dividing resistors in the
second embodiment, and the like may be appropriately changed
according to the individual design. The voltage values may also be
appropriately changed according to the individual design. The
target for detecting the rotation angle is not limited to the drive
motor of the electric vehicle.
[0107] Although the present disclosure has been made in accordance
with the embodiments, it is understood that the present disclosure
is not limited to such embodiments and configurations. The present
disclosure covers various modification examples and equivalent
arrangements. In addition, various combinations and forms, and
further, other combinations and forms including only one element,
or more or less than these elements are also within the scope and
the scope of the present disclosure.
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